The present invention relates to a colour cathode ray tube device in which the screen section is divided in a plurality of sub-regions and means for separately scanning the sub-regions.
In recent years there has been considerable research aimed at meeting demands relating to high definition colour cathode ray tube or associated large-screen high resolution colour cathode ray tubes. One requirement for achieving in such tubes is that the electron beam spot on the screen is made smaller. There have also been efforts in the past to improve the electron gun electrode structure and to lengthen and increase the size and aperture of actual electron guns, but results achieved so far have been unsatisfactorily. The main reason for this is that the electron gun-to-screen distance becomes larger as a cathode ray tube becomes larger. Thus, the electron gun magnification becomes too large. According, reducing the electron gun-to-screen distance is an important aspect of achieving high resolution. Methods for wide-angle deflection are not practical for this purpose, since they result in an increased difference in magnification between central and peripheral portions of the screen.
In response to this drawback, a structure in which the screens of a plurality of horizontally disposed, independent CRT""s are combined into a unitary screen has been proposed in Japanese Utility Model Publication No. 39-25641, Japanese Patent Publication No. 42-4928 and Japanese Patent Disclosure No. 50-17167.
These known structures have, however, the problem that joints are visible between the independent colour cathode ray tubes.
It is an object of the invention to provide a cathode ray tube in which the above mentioned problem is reduced or overcome.
To this end a cathode ray tube device in accordance with the invention is characterized in that device comprises a single colour cathode ray tube which has, arranged in a linear arrangement, a multitude of necks, deflection yokes and electron guns, but only one shadowmask.
When colour displays are provided by tubes such as this, in which the screen section is a unitary section and divided scanning is effected, a colour cathode ray tube employing a single shadow mask system for colour selection permits simple, but sure, colour selection and is very practical.
A colour cathode ray tube employing a multi-neck system such as this with a unitary screen structure makes it possible to produce an image that is easy to view, since it eliminates the joints between adjacent cathode ray tubes which occur with an array of independent cathode ray tubes, as described above. The necks are all aligned in a linear arrangement, i.e. substantially along a single line. Preferably an improved image uniformity is obtained by creating a partial overlap of two images created in two adjacent sub-regions. The preferred number of sub-regions is two or three. When two sub-regions are scanned (and thus only two inkiest, deflection units etc are used) the device is relatively simple. As the number of sub-regions increase the device gets more complicated. The use of three sub-regions has the advantage that the overlap regions are not in the middle of the image, whereby the change of annoying visibility of the overlap regions is reduced, while the device as a whole is relatively simple, be it more complicated then for two sub-regions.
The purpose of the invention is to create a CRT with a reduced depth. Other concepts for reduced-depth CRT displays, like the Matsushita xe2x80x9cFlat Visionxe2x80x9d, deviate so much from a conventional CRT that they cannot be manufactured in a normal CRT factory. An approach, in which a two dimensional array of many yokes are used, also deviates significantly from a normal CRT. The cathode ray tube in accordance with the invention requires much less deviation from normal techniques.